1. Field of the Invention
The present invention relates to pivotal hand tools with cooperating jaws, such as pliers, cutters or the like, and, in particular, to a pivot joint therefor.
2. Description of the Prior Art
There are many types of pivotal hand tools, such as various types of pliers and cutters, and they all typically include a pair of lever members each having a handle portion at one end and a jaw portion at the other end and arranged in intersecting relationship for pivotal movement about a pivot axis through the point of intersection so that the jaw portions cooperate with each other. Various types of pivot joints are provided for such hand tools. A common type of joint involves arranging the lever members in overlapping relationship with aligned openings therethrough and a pivot member extending through the aligned openings. In one such arrangement a rivet extends through the aligned openings to define a pivot pin. But in this kind of pivot joint the rivet must be formed of a relatively soft material so that the rivet can be deformed after insertion through the aligned openings to lock it in place on the assembly. This means that the rivet cannot be heat treated before assembly and that the finished hand tool must be heat treated after it has been assembled. Heat treatment after assembly often causes the lever members or tool halves to " lock" together, a situation which is commonly manually corrected with the use of a hammer and anvil. This is a considerable inconvenience.
An alternative pivot joint which does not use rivets involves interlocking threaded fasteners extending through the aligned openings to form the pivot member. One such arrangement utilizes frustoconical threaded members disposed in chamfered openings through the lever members so that drawing the two threaded members together will serve to clamp the lever members together. But this arrangement creates considerable wear on the threaded pivot members.
An alternative threaded pivot arrangement utilizes two headed cylindrical pivot members, one male and one female, but in this type of joint the threaded pivot members and the lever members must be designed to very close tolerances so that they will hold the lever members securely together with just the right degree of tightness. Furthermore, such threaded joints have a tendency to loosen during use and must be periodically tightened to maintain the proper degree of tightness.